Disentangling magnetic and environmental signatures of sedimentary 10Be/9Be records

Reconstructions of the global production rate of the cosmogenic isotope 10Be from sedimentary records of authigenic 10Be/9Be ratios have been successfully used to obtain independent estimates of geomagnetic dipole moment variations caused by field excursions or reversals. In this study, we assess th...

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Bibliographic Details
Published in:Quaternary Science Reviews
Main Authors: Savranskaia, Tatiana, Egli, Ramon, Valet, Jean-pierre, Bassinot, Franck, Meynadier, Laure, Bourlès, Didier L., Simon, Quentin, Thouveny, Nicolas
Format: Text
Language:English
Published: Elsevier BV
Subjects:
geo
Online Access:https://doi.org/10.1016/j.quascirev.2021.106809
https://archimer.ifremer.fr/doc/00682/79399/81939.pdf
https://archimer.ifremer.fr/doc/00682/79399/81940.pdf
https://archimer.ifremer.fr/doc/00682/79399/81941.pdf
https://archimer.ifremer.fr/doc/00682/79399/81942.pdf
https://archimer.ifremer.fr/doc/00682/79399/
Description
Summary:Reconstructions of the global production rate of the cosmogenic isotope 10Be from sedimentary records of authigenic 10Be/9Be ratios have been successfully used to obtain independent estimates of geomagnetic dipole moment variations caused by field excursions or reversals. In this study, we assess the reliability of 10Be/9Be as a proxy for the cosmogenic 10Be production rate by evaluating two potential biasing sources represented by sediment composition and climatic modulation. For this purpose, we compare five high-resolution 10Be/9Be records of the Matuyama-Brunhes (M-B) field reversal from sediment cores of the Indian, West Pacific, and North Atlantic oceans. Significant increase of 10Be/9Be ratios at 774 ka is explained in terms of the dominant control of geomagnetic modulation during the M-B reversal. Results do not support the existence of a direct proportionality between measured sedimentary 10Be/9Be ratio and cosmogenic 10Be production rate, as shown by 10Be/9Be records that offset relative to each other during and outside the M-B reversal. Residual differences between offset-corrected rescaled records do not appear to be related to an incomplete correction of variable sediment scavenging efficiencies by 9Be normalization. Instead, these differences can be explained by a common climatic modulation model, assuming a linear relation between 10Be/9Be and the global 10Be production rate with site- and time-dependent additive and multiplicative coefficients. These coefficients are linear functions of a single global climate proxy identified with the benthic O record. Additive coefficients are almost constant in time and can represent up to 60% of the average 10Be/9Be value during periods of stable field polarity. Multiplicative coefficients are also site-specific, with mean values representing the bulk scavenging efficiency of the site, and variations about this mean expressing a multiplicative climatic modulation of the 10Be production rate. The amplitude of this modulation amounts to 10–15% of the maximum ...